AMDGPU: Fix asserting when trying to print scc (llvm#101175)

This is printable using inline assembly. Also we should
handle using scc directly as instruction operands.

(cherry picked from commit d2b6a8e)
Change-Id: I61dc2fd91563b66cdbabbe077acd79ba4be29680

Author: arsenm

llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUInstPrinter.cpp

@@ -372,8 +372,6 @@ void AMDGPUInstPrinter::printRegOperand(unsigned RegNo, raw_ostream &O,
   case AMDGPU::SP_REG:
   case AMDGPU::PRIVATE_RSRC_REG:
     llvm_unreachable("pseudo-register should not ever be emitted");
-  case AMDGPU::SCC:
-    llvm_unreachable("pseudo scc should not ever be emitted");
   default:
     break;
   }

llvm/test/CodeGen/AMDGPU/inline-asm.ll

@@ -314,3 +314,21 @@ exit:
   tail call void asm sideeffect "; use $0", "v"(i64 %v1)
   ret void
 }
+
+; CHECK-LABEL: {{^}}scc_as_i32:
+; CHECK: ; def scc
+; CHECK: ; use scc
+define void @scc_as_i32() {
+  %scc = call i32 asm sideeffect "; def $0", "={scc}"()
+  call void asm sideeffect "; use $0 ", "{scc}"(i32 %scc)
+  ret void
+}
+
+; CHECK-LABEL: {{^}}scc_as_i1:
+; CHECK: ; def scc
+; CHECK: ; use scc
+define void @scc_as_i1() {
+  %scc = call i1 asm sideeffect "; def $0", "={scc}"()
+  call void asm sideeffect "; use $0 ", "{scc}"(i1 %scc)
+  ret void
+}